Physical Mechanisms of Magnetic Field Effects on the Dielectric Function of Hybrid Magnetorheological Suspensions

In this paper, we study the electrical properties of new hybrid magnetorheological suspensions (hMRSs) and propose a theoretical model to explain the dependence of the electric capacitance on the iron volumetric fraction, ΦFe, of the dopants and on the external magnetic field. The hMRSs, with dimensions of 30 mm×30 mm×2 mm, were manufactured based on impregnating cotton fabric, during heating, with three solutions of iron microparticles in silicone oil. Flat capacitors based on these hMRSs were then produced. The time variation of the electric capacitance of the capacitors was measured in the presence and absence of a magnetic field, B, in a time interval of 300 s, with Δt=1 s steps. It was shown that for specific values of ΦFe and B, the coupling coefficient between the cotton fibers and the magnetic dipoles had values corresponding to very stable electrical capacitance. Using magnetic dipole approximation, the mechanisms underlying the observed phenomena can be described if the hMRSs are considered continuous media.

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Graphene Platelets-Based Magnetoactive Materials with Tunable Magnetoelectric and Magnetodielectric Properties

Nanomaterials ◽

10.3390/nano10091783 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1783

Author(s):

Ioan Bica ◽

Eugen Mircea Anitas

Keyword(s):

Magnetic Field ◽

Silicone Oil ◽

Dielectric Materials ◽

Cotton Fibers ◽

Magnetic Flux Density ◽

Electrical Capacitance ◽

Medium Frequency ◽

Physical Mechanisms ◽

Electrical Devices ◽

Living Organisms

We fabricate hybrid magnetoactive materials (hMAMs) based on cotton fibers, silicone oil, carbonyl iron and graphene nanoplatelets (nGr) at various mass concentrations ΦnGr. The obtained materials are used as dielectric materials for manufacturing plane electrical capacitors. The equivalent electrical capacitance Cp and resistance Rp are measured in an electric field of medium frequency f, without and respectively with a magnetic field of magnetic flux density B in the range from 0.1 T up to 0.5 T. The results are used to extract the components ϵr′ and ϵr″ of the complex relative permittivity ϵr*, and to reveal the magnitude of the induced magnetoelectric couplings kx and magnetodielectric effects MDE. It is shown that ϵr′, ϵr″, kx and MDE are significantly influenced by f,B and ΦnGr. We describe the underlying physical mechanisms in the framework of dipolar approximation and using elements of dielectric theory. The tunable magnetoelectric and magnetodielectric properties of hMAMs are useful for manufacturing electrical devices for electromagnetic shielding of living organisms.

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Magnetorheological Hybrid Elastomers Based on Silicone Rubber and Magnetorheological Suspensions with Graphene Nanoparticles: Effects of the Magnetic Field on the Relative Dielectric Permittivity and Electric Conductivity

International Journal of Molecular Sciences ◽

10.3390/ijms20174201 ◽

2019 ◽

Vol 20 (17) ◽

pp. 4201 ◽

Cited By ~ 4

Author(s):

Bica ◽

Bunoiu

Keyword(s):

Magnetic Field ◽

Dielectric Permittivity ◽

Silicone Rubber ◽

Silicone Oil ◽

Relative Dielectric Permittivity ◽

Magnetorheological Elastomers ◽

Magnetorheological Suspensions ◽

Alternating Electric Field ◽

Graphene Nanoparticles ◽

The Magnetic Field

Hybrid magnetorheological elastomers (hMREs) were manufactured based on silicone rubber, silicone oil, carbonyl iron microparticles, graphene nanoparticles and cotton fabric. Using the hMREs, flat capacitors (FCs) were made. Using the installation described in this paper, the electrical capacitance and the coefficient of dielectric losses of the hMREs were measured as a function of the intensity of the magnetic field superimposed over an alternating electric field. From the data obtained, the electrical conductivity, the relative dielectric permittivity and magnetodielectric effects are determined. It is observed that the obtained quantities are significantly influenced by the intensity of the magnetic field and the amount of graphene used.

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Experimental and Theoretical Study of the Field Induced Phase Separation in Electro- and Magnetorheological Suspensions

International Journal of Modern Physics B ◽

10.1142/s0217979299001806 ◽

1999 ◽

Vol 13 (14n16) ◽

pp. 1791-1797 ◽

Cited By ~ 3

Author(s):

S. Cutillas ◽

G. Bossis ◽

E. Lemaire ◽

A. Meunier ◽

A. Cebers

Keyword(s):

Magnetic Field ◽

Phase Separation ◽

Theoretical Study ◽

Silicone Oil ◽

The Other ◽

Regular Pattern ◽

Normal Stresses ◽

Dense Phase ◽

Magnetorheological Suspensions ◽

The Magnetic Field

We present here the study of field induced phase separation in E.R. and M.R. fluids. Two thermodynamic models — one for the formation of chais of particles and the other for phase separation are presented and compared with experimental results obtained with two kinds of suspensions. One was made of silica particles in silicone oil and the other was made of magnetic polystyrene particles in water. In the presence of a flow the phase separation occurs with the dense phase forming a regular pattern of stripes. The dependence of the period of these stripes on the intensity of the magnetic field is well reproduced by the same kind of thermodynamic model if we add the effect of normal stresses induced by the shear flow.

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Gelatine-Coated Carbonyl Iron Particles and Their Utilization in Magnetorheological Suspensions

Materials ◽

10.3390/ma14102503 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2503

Author(s):

Tomas Plachy ◽

Patrik Rohrer ◽

Pavlina Holcapkova

Keyword(s):

Magnetic Field ◽

Liquid Medium ◽

Carbonyl Iron ◽

Magnetic Particles ◽

Silicone Oil ◽

Rheological Parameters ◽

Iron Particles ◽

Magnetorheological Suspensions ◽

Magnetorheological Suspension ◽

Dynamic Yield

This study demonstrates the formation of biocompatible magnetic particles into organized structures upon the application of an external magnetic field. The capability to create the structures was examined in silicone-oil suspensions and in a gelatine solution, which is commonly used as a blood plasma expander. Firstly, the carbonyl iron particles were successfully coated with gelatine, mixed with a liquid medium in order to form a magnetorheological suspension, and subsequently the possibility of controlling their rheological parameters via a magnetic field was observed using a rotational rheometer with an external magnetic cell. Scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis confirmed the successful coating process. The prepared magnetorheological suspensions exhibited a transition from pseudoplastic to Bingham behavior, which confirms their capability to create chain-like structures upon application of a magnetic field, which thus prevents the liquid medium from flowing. The observed dynamic yield stresses were calculated using Robertson–Stiff model, which fit the flow curves of the prepared magnetorheological suspensions well.

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Hybrid Magnetorheological Composites for Electric and Magnetic Field Sensors and Transducers

Nanomaterials ◽

10.3390/nano10102060 ◽

2020 ◽

Vol 10 (10) ◽

pp. 2060

Author(s):

Ioan Bica ◽

Eugen Mircea Anitas ◽

Liviu Chirigiu

Keyword(s):

Magnetic Field ◽

Silicone Oil ◽

Low Cost ◽

Relative Dielectric Constant ◽

Dielectric Materials ◽

Electrical Capacitance ◽

Magnetic Dipoles ◽

Magnetic Field Sensors ◽

Electrical Devices ◽

Recorded Data

We present a simple, low-cost, and environmental-friendly method for the fabrication of hybrid magnetorheological composites (hMCs) based on cotton fibers soaked with a mixture of silicone oil (SO), carbonyl iron (CI) microparticles, and iron oxide microfibers (μF). The obtained hMCs, with various ratios (Φ) of SO and μF, are used as dielectric materials for manufacturing electrical devices. The equivalent electrical capacitance and resistance are investigated in the presence of an external magnetic field, with flux density B. Based on the recorded data, we obtain the variation of the relative dielectric constant (ϵr′), and electrical conductivity (σ), with Φ, and B. We show that, by increasing Φ, the distance between CI magnetic dipoles increases, and this leads to significant changes in the behaviour of ϵr′ and σ in a magnetic field. The results are explained by developing a theoretical model that is based on the dipolar approximation. They indicate that the obtained hMCs can be used in the fabrication of magneto-active fibers for fabrication of electric/magnetic field sensors and transducers.

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Study of Vegetative Reactions of Egyptian and Ugro-Finnic Ethnic Groups under the Influence of Alternating Magnetic Field Effects and Different Climatic and Geographical Conditions

International Journal of Psychosocial Rehabilitation ◽

10.37200/ijpr/v24i3/pr2020348 ◽

2020 ◽

Vol 24 (3) ◽

pp. 3226-3256

Author(s):

Guriy I. Mikita

Keyword(s):

Magnetic Field ◽

Ethnic Groups ◽

Alternating Magnetic Field ◽

Magnetic Field Effects ◽

Field Effects

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Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

Sustainability ◽

10.3390/su13095086 ◽

2021 ◽

Vol 13 (9) ◽

pp. 5086

Author(s):

Fatih Selimefendigil ◽

Hakan F. Oztop ◽

Ali J. Chamkha

Keyword(s):

Magnetic Field ◽

Heat Transfer ◽

Particle Size ◽

Aspect Ratio ◽

Power Law ◽

Volume Fraction ◽

Inclined Magnetic Field ◽

Magnetic Field Effects ◽

Power Law Nanofluid ◽

Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

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